Attack Piece Blocks are blocks from Mario and Luigi: Bowser's Inside Story with the letter A in them, most likely standing for attack.
Attack Piece Blocks are scattered throughout Bowser's Body and in places outside Bowser such as Dimble Wood. There are ten in almost every area and will give Mario and Luigi an Attack Piece if struck. Hitting all ten will give the bros. a new Special Move. Bowser can not strike these blocks.